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Bahramy, M. ,S.,Clark, O. ,J.,Yang, B.-J.,Feng, J.,Bawden, L.,Riley, J. ,M.,Marković,, I.,Mazzola, F.,Sunko, V.,Biswas, D.,Cooil, S. ,P.,Jorge, M.,Wells, J. ,W.,Leandersson, M Nature Publishing Group, a division of Macmillan P 2018 NATURE MATERIALS Vol.17 No.1
Transition-metal dichalcogenides (TMDs) are renowned for their rich and varied bulk properties, while their single-layer variants have become one of the most prominent examples of two-dimensional materials beyond graphene. Their disparate ground states largely depend on transition metal d-electron-derived electronic states, on which the vast majority of attention has been concentrated to date. Here, we focus on the chalcogen-derived states. From density-functional theory calculations together with spin- and angle-resolved photoemission, we find that these generically host a co-existence of type-I and type-II three-dimensional bulk Dirac fermions as well as ladders of topological surface states and surface resonances. We demonstrate how these naturally arise within a single p-orbital manifold as a general consequence of a trigonal crystal field, and as such can be expected across a large number of compounds. Already, we demonstrate their existence in six separate TMDs, opening routes to tune, and ultimately exploit, their topological physics.
Mechanistic study of styrene aziridination by iron( <small>IV</small> ) nitrides
Crandell, Douglas ,W.,Muñ,oz III, Salvador B.,Smith, Jeremy M.,Baik, Mu-Hyun Royal Society of Chemistry 2018 Chemical Science Vol.9 No.45
<▼1><P>A combined experimental and computational investigation reveals that styrene aziridination by an iron(<SMALL>IV</SMALL>) nitride occurs by a stepwise mechanism involving multistate character.</P></▼1><▼2><P>A combined experimental and computational investigation was undertaken to investigate the mechanism of aziridination of styrene by the tris(carbene)borate iron(<SMALL>IV</SMALL>) nitride complex, PhB(<SUP><I>t</I></SUP>BuIm)<SUB>3</SUB>Fe 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 N. While mechanistic investigations suggest that aziridination occurs <I>via</I> a reversible, stepwise pathway, it was not possible to confirm the mechanism using only experimental techniques. Density functional theory calculations support a stepwise radical addition mechanism, but suggest that a low-lying triplet (<I>S</I> = 1) state provides the lowest energy path for C–N bond formation (24.6 kcal mol<SUP>–1</SUP>) and not the singlet ground (<I>S</I> = 0) state. A second spin flip may take place in order to facilitate ring closure and the formation of the quintet (<I>S</I> = 2) aziridino product. A Hammett analysis shows that electron-withdrawing groups increase the rate of reaction <I>σ</I><SUB>p</SUB> (<I>ρ</I> = 1.2 ± 0.2). This finding is supported by the computational results, which show that the rate-determining step drops from 24.6 kcal mol<SUP>–1</SUP> to 18.3 kcal mol<SUP>–1</SUP> when (<I>p</I>-NO<SUB>2</SUB>C<SUB>6</SUB>H<SUB>4</SUB>)CH 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 CH<SUB>2</SUB> is used and slightly increases to 25.5 kcal mol<SUP>–1</SUP> using (<I>p</I>-NMe<SUB>2</SUB>C<SUB>6</SUB>H<SUB>4</SUB>)CH 00000000000
Davies, Daniel ,W.,Butler, Keith T.,Skelton, Jonathan M.,Xie, Congwei,Oganov, Artem R.,Walsh, Aron Royal Society of Chemistry 2018 Chemical Science Vol.9 No.4
<▼1><P>The standard paradigm in computational materials science is INPUT: <SMALL>STRUCTURE;</SMALL> OUTPUT: <SMALL>PROPERTIES</SMALL>, which has yielded many successes but is ill-suited for exploring large areas of chemical and configurational hyperspace.</P></▼1><▼2><P>The standard paradigm in computational materials science is INPUT: S<SMALL>TRUCTURE</SMALL>; OUTPUT: P<SMALL>ROPERTIES</SMALL>, which has yielded many successes but is ill-suited for exploring large areas of chemical and configurational hyperspace. We report a high-throughput screening procedure that uses compositional descriptors to search for new photoactive semiconducting compounds. We show how feeding high-ranking element combinations to structure prediction algorithms can constitute a pragmatic computer-aided materials design approach. Techniques based on structural analogy (data mining of known lattice types) and global searches (direct optimisation using evolutionary algorithms) are combined for translating between chemical composition and crystal structure. The properties of four novel chalcohalides (Sn<SUB>5</SUB>S<SUB>4</SUB>Cl<SUB>2</SUB>, Sn<SUB>4</SUB>SF<SUB>6</SUB>, Cd<SUB>5</SUB>S<SUB>4</SUB>Cl<SUB>2</SUB> and Cd<SUB>4</SUB>SF<SUB>6</SUB>) are predicted, of which two are calculated to have bandgaps in the visible range of the electromagnetic spectrum.</P></▼2>
Compensatory Neural Reorganization in Tourette Syndrome
Jackson, Stephen ,R.,Parkinson, Amy,Jung, Jeyoung,Ryan, Suzanne ,E.,Morgan, Paul ,S.,Hollis, Chris,Jackson, Georgina ,M. Cell Press 2011 Current biology Vol.21 No.7
<P><B>Summary</B></P><P>Children with neurological disorders may follow unique developmental trajectories whereby they undergo compensatory neuroplastic changes in brain structure and function that help them gain control over their symptoms [1–6]. We used behavioral and brain imaging techniques to investigate this conjecture in children with Tourette syndrome (TS). Using a behavioral task that induces high levels of intermanual conflict, we show that individuals with TS exhibit enhanced control of motor output. Then, using structural (diffusion-weighted imaging) brain imaging techniques, we demonstrate widespread differences in the white matter (WM) microstructure of the TS brain that include alterations in the corpus callosum and forceps minor (FM) WM that significantly predict tic severity in TS. Most importantly, we show that task performance for the TS group (but not for controls) is strongly predicted by the WM microstructure of the FM pathways that lead to the prefrontal cortex and by the functional magnetic resonance imaging blood oxygen level-dependent response in prefrontal areas connected by these tracts. These results provide evidence for compensatory brain reorganization that may underlie the increased self-regulation mechanisms that have been hypothesized to bring about the control of tics during adolescence.</P>
Granulin Is a Soluble Cofactor for Toll-like Receptor 9 Signaling
Park, Boyoun,Buti, Ludovico,Lee, Sungwook,Matsuwaki, Takashi,Spooner, Eric,Brinkmann, Melanie ,M.,Nishihara, Masugi,Ploegh, Hidde ,L. Elsevier 2011 Immunity Vol.34 No.4
<P><B>Summary</B></P><P>Toll-like receptor (TLR) signaling plays a critical role in innate and adaptive immune responses and must be tightly controlled. TLR4 uses LPS binding protein, MD-2, and CD14 as accessories to respond to LPS. We therefore investigated the presence of an analagous soluble cofactor that might assist in the recruitment of CpG oligonucleotides (CpG-ODNs) to TLR9. We report the identification of granulin as an essential secreted cofactor that potentiates TLR9-driven responses to CpG-ODNs. Granulin, an unusual cysteine-rich protein, bound to CpG-ODNs and interacted with TLR9. Macrophages from granulin-deficient mice showed not only impaired delivery of CpG-ODNs to endolysosomal compartments, but also decreased interaction of TLR9 with CpG-ODNs. As a consequence, granulin-deficient macrophages showed reduced responses to stimulation with CpG-ODNs, a trait corrected by provision of exogenous granulin. Thus, we propose that granulin contributes to innate immunity as a critical soluble cofactor for TLR9 signaling.</P> <P><B>Highlights</B></P><P>► Granulin binds TLR9 and CpG oligonucleotides ► Granulin is sufficient for intracellular localization of CpG-ODNs ► Granulin is a critical cofactor in enabling TLR9 signal transduction</P>
Dynamic assembly of Hda and the sliding clamp in the regulation of replication licensing
Kim, Jin S.,Nanfara, Michael T.,Chodavarapu, Sundari,Jin, Kyeong S.,Babu, Vignesh ,M. ,P.,Ghazy, Mohamed A.,Chung, Scisung,Kaguni, Jon M.,Sutton, Mark D.,Cho, Yunje Oxford University Press 2017 Nucleic acids research Vol.45 No.7
<P><B>Abstract</B></P><P>Regulatory inactivation of DnaA (RIDA) is one of the major regulatory mechanisms of prokaryotic replication licensing. In RIDA, the Hda–sliding clamp complex loaded onto DNA directly interacts with adenosine triphosphate (ATP)-bound DnaA and stimulates the hydrolysis of ATP to inactivate DnaA. A prediction is that the activity of Hda is tightly controlled to ensure that replication initiation occurs only once per cell cycle. Here, we determined the crystal structure of the Hda–β clamp complex. This complex contains two pairs of Hda dimers sandwiched between two β clamp rings to form an octamer that is stabilized by three discrete interfaces. Two separate surfaces of Hda make contact with the β clamp, which is essential for Hda function in RIDA. The third interface between Hda monomers occludes the active site arginine finger, blocking its access to DnaA. Taken together, our structural and mutational analyses of the Hda–β clamp complex indicate that the interaction of the β clamp with Hda controls the ability of Hda to interact with DnaA. In the octameric Hda–β clamp complex, the inability of Hda to interact with DnaA is a novel mechanism that may regulate Hda function.</P>